<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <li>4</li>
    <li>5</li>
    <li>6</li>
    <li>7</li>
    <li>8</li>
    <li>9</li>
    <li>10</li>
  </ul>
  <script>
  var ul = document.getElementsByTagName('ul')[0];
  //事件委托
   ul.onclick = function() {
     
     console.log(event.target.innerHTML);
   }
  //点击一次
  // ul.addEventListener('click', function(event) {
  //   console.log('点击了一次',event);
  // },{once:true})
  </script>
</body>
</html>